Exited-state quantum phase transitions in constrained systems
Exited-state quantum phase transitions in constrained systems
We extend the standard semiclassical theory of Exited-State Quantum Phase Transitions (ESQPTs), based on a classification of stationary points in the classical Hamiltonian, to constrained systems. We adopt the method of Lagrange multipliers to find all stationary points and their properties directly from the Hamiltonian constrained by an arbitrary number …